Fast developement of analytical techniques allows us to observe even a single molecule on the surface. We need not only excellent detection tools - we also need to enhance the optical response of the molecules. Excellent tools for single molecule investigations are: SERS (Surface Enhancement Raman Scattering) and MEF (Metal Enhanced Fluorescence). The use of plain, rough or nanostructured metallic surfaces in both methods provides dramatically strong enhancement of Raman or fluorescence signal, respectively. These techniques have been sucessfully used in the study of biomolecules, for example single DNA observations and drug detection. My work is devoted to SERS and MEF investigations of porphyrin isomers - so called porphycenes. The absorption spectra of these molecules overlap with plasmon resonance bands of metals. Most of my work is focused on preparing well-characterized metallic (nanostructured) surface, and attaching molecules to the metal nanostructures.
Depending on surface structure, and, most important, the distance between molecules and the metal (especially - silver or gold), we are able to observe SERS, SERRS or, hopefully soon, MEF effects. At close proximity to the surface, extinguished fluorescence and enhanced Raman signal (SERS, SERRS) dominate. But when polymer spacer (from several up to hundreds of nanometers thick) is present, metal enhanced fluorescence is expected to appear. Single molecule spectroscopy on the metalic surfaces has great potential in modern analytic chemistry, as a base for construction of lab-on-chip devices.
|